BSR56 JFET — Specifications & Equivalents

About the BSR56

The BSR56 is an N-channel JFET with a drain–source voltage (V_DS) rating of 40 V, a continuous drain current (I_D) of 0.05 A and an on-resistance (R_DS(on)) of 25 Ω. It can dissipate up to 0.25 W and is rated to a junction temperature of 150 °C. It is supplied in the SOT23 package.

At a glance

• Type: N-channel JFET
• Max drain–source voltage (V_DS): 40 V
• Max continuous drain current (I_D): 0.05 A
• On-resistance (R_DS(on)): 25 Ω
• Power dissipation (P_D): 0.25 W
• Max junction temperature (T_J): 150 °C
• Package: SOT23

Typical applications

With its 40 V drain–source rating the BSR56 sits in the low-voltage class of switching MOSFETs, typically found in 12 V and 24 V automotive and industrial rails, synchronous buck converters, load switching and reverse-polarity protection and H-bridges for small motors.

At 0.05 A it is aimed at small-signal and light-load switching rather than power conversion.

On-resistance of 25 Ω is relatively high, so this part is better suited to low duty-cycle or low-current switching than to continuous high-current conduction.

Choosing a replacement for the BSR56

A drop-in substitute for the BSR56 must be the same N-channel type and offer a drain–source rating of at least 40 V, a continuous drain current rating of at least 0.05 A and an on-resistance no higher than 25 Ω if efficiency and heat matter.

Mechanically, check the replacement against the SOT23 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Where the application switches inductive loads or runs near the voltage limit, keep extra headroom rather than choosing a part that only just meets the original numbers.

Frequently asked questions

What is the BSR56?

The BSR56 is an N-channel junction field-effect transistor (JFET). It is rated for 40 V drain-source and 0.05 A continuous drain current.

What is the maximum voltage of the BSR56?

The BSR56 has a maximum drain-source voltage (Vds) of 40 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.

How much current can the BSR56 handle?

It is rated for 0.05 A of continuous drain current, with power dissipation limited to 0.25 W. Real-world capability depends on your heatsinking and ambient temperature.

What is the on-resistance of the BSR56?

On-resistance (Rds(on)) is 25 Ω. Multiply by the square of your load current to estimate conduction loss.

What package does the BSR56 come in?

It is listed in SOT23. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the BSR56?

No verified equivalents are listed yet. Choose a part of the same polarity that meets or exceeds every rating above and shares a compatible package and pinout.